As materials for forming an antireflection film, for example, heat-curable type polysiloxane compositions are known, and they are disclosed in JP-A-61-247743, JP-A-6-25599, JP-A-7-331115, JP-A-10-232301 and so forth.
However, antireflection films obtained by using such heat-curable type polysiloxane compositions are formed with a layer continuous in the planar direction, and therefore they have a problem that they suffer from insufficient antiscratching property and as a result, insufficient durability.
Further, in the production of such antireflection films, a heat treatment at a high temperature for a long period of time is required. Thus, they suffer from problems of low productivity and limited types of applicable substrates.
Therefore, as disclosed in JP-A-8-94806, an optically functional film has been proposed which is prepared by laminating a high refractive index film comprising fine particles localized in a high refractive index binder resin and formed as a layer continuous in the planer direction and a low refractive index film made of a fluorine type copolymer in this order on a substrate.
More specifically, for forming the high refractive index film as a continuous layer, a layer of fine particles such as metal oxide particles having a diameter of 200 nm or less is formed on process paper in advance, and the layer is then pressed onto the high refractive index binder resin on the substrate to embed the fine particle layer in the high refractive index binder resin and thereby localize the fine particles.
Further, the low refractive index film is formed by curing a resin composition comprising 100 parts by weight of a fluorine-containing copolymer formed by copolymerizing of a monomer composition containing 30 to 90% by weight of vinylidene fluoride and 5 to 50% by weight of hexafluoropropylene, and having a fluorine content of 60 to 70% by weight, 30 to 150 parts by weight of a polymerizable compound having an ethylenically unsaturated group and a polymerization initiator in an amount of 0.5 to 10 parts by weight with respect to the total weight of the fluorine-containing copolymer and the polymerizable compound taken as 100 parts by weight to form a thin film having a film thickness of 200 nm or less.
However, the process of producing the high refractive index film of the optically functional film disclosed in JP-A-8-94806 as a continuous layer is complicated, and as a result, it is difficult to prepare an optically functional film exhibiting uniform characteristics.
Furthermore, in such an optically functional film, surface toughness of the low refractive index film, relationship thereof with film thickness and surface roughness value of the high, refractive index film are not taken into consideration, and therefore it suffers from a problem of insufficient antiscratching property of the low refractive index film.